Rotary kiln and method of freeing same of a fire ring therein



Dec 7, 1965 KAzuNoRl NAKAHARA 3,222,222

ROTARY KILN AND METHOD OF FREEING SAME 0F A FIRE RING THEREIN 2 Sheets-Sheet l Filed Aug. 28, 1961 g rlllllllllllllln/Illalll Sii INVENTOK KAZUNORI NAKAHARA Dec. 7, 1965 KAzuNoRl NAKAHARA 3,222,222

ROTARY KILN AND METHOD 0F FREEING REIN SAME OF A FIRE RING THE Filed Aug. 28, 1961` 2 Sheets-Sheet 2 u* 'y ,2 /Z /3 Fig. 6

OPER E TE /M BLOW-OFF TEMP ,y J' I /f DAYS OF OPERATION Fig.7

INVENTOR.

KAZUNORI NAKAHARA /76 ffr, M7'

United States Patent O 3,222,222 ROTARY KILN AND METHOD F FREEING SAME 0F A FIRE RING THEREIN Kazunori Nakahara, Sho'chiku-kan, Aza Hikage, Rokugo-mura, Azuma-gun, Japan Filed Aug. 28, 1961, Ser. No. 134,476

Claims priority, application Japan, Sept. 9, 1960,

SiS/37,839 5 Claims. (Cl. 134-22) manufacturing method by the use of a rotary kiln of'4 conventional type, some undesirable deposit or other is very likely to grow around the inner lining of the kiln during lthe operation, thus being detrimental to the normal progress of operation and standing very much in the way of economical operation which may be called a cancer in the operation of the rotary kiln.

As shown in the accompanying drawing, FIG. 1, such deposit around the inner wall of the rotary kiln may grow up until it prevents the ventilation of the rotary kiln so that the combustion of the burner may be lowered thereby lowering the temperature inside the kiln and reducing the speed of work production, finally leading to reduction in manufacturing capacity and so much increase in manufacturing unit cost.

In order to remove such deposit at the inner wall of `the rotary kiln and prevent its formation in good time,

various procedures have been attempted up to now. For instance, an excessive supply of coke may be thrown into the rotary kiln with the result that the normal supply of work has to be suspended for a while or may be reduced and moreover the temperature around the deposit may be enhanced or a scraper is employed to scrape oit such deposit in the rotary kiln mechanically or a kiln gun `to hit the deposit for removal.

However, the first method as mentioned above will necessitate the suspension'of normal supply of work for a while or lessen its supply so that the output of production may be not `only. lowered but also large expenses :incurred by the use of excessive amounts of coke.

The second method involves such a defect as the output of production may decrease during the period of adjustment of the burner and to make the 'matter worse, sufficient work cannot be achieved in spite of large consumption of coke. According to the third and fourth methods, some mechanical means of high cost may be required to achieve the original purpose and yet no good results can be expected. With these drawbacks behind none of all t-he above mentioned methods has proved successful from'an industrial point of view.

According to the present invention, it is .fpossible to keep the rotary kiln during its operation always running by simple means for the purpose of removing such deposit inside the rotary kiln thereby obtaining a very eifective operation of the kiln. There are provided a suitable number of pierced bores at such places at suitable intervals as the for-mation of deposit can be expected in the inner wall of the rotary kiln, said bores being filled with some wadding or operative elements -beforehand and then said elements are pushed inwardly either by hand or mechanical means during the operation of the rotary kiln at any time, depending on the formation of deposits thereby destroying and removing said deposits.4 Alternately, there are also .provided a suitable number of pierced bores at such places at suitable intervals as the formation of deposits is expected, said bores being filled with y operative elements and moreover said operative elements 3,222,222 Patented Dec. 7, 1965 ice same in cross section along the line A-A. FIG. 2

shows an arrangement of pierced bores and operative elements at such places of the inner wall of a rotary kiln as the -formation of deposits can be expected. FIG. 3 shows the condition of a rotary kiln after removing said kind of deposit by means of operative elements. I of FIG. 3 is a view of the same in longitudinal section and II is another view of the same in cross section along the line B-B. FIG. 4 shows the arrangement of a brace of metal around the outer circumference of a pierced bore withreference to FIG. 2. FIG. 5 is a combination view of operative element and gun powder. FIG. 6 shows the condition of a rotary kiln after replacing an operative element with a gunpowder element and removing said deposit from inside the kiln by explosion.

FIG. 7 is a diagrammatical view showing the conventional condition of operation in conventional processes.

Based on the accompanying drawings, the first method of operation will be furt-her explained. As shown in FIG. 2, the wall of a rotary kiln is usually composed of an iron cylindrical wall 1 and a refractory lining 2. A bore 3 of 1.5 =or thereabouts is already disposed at such a place inside the kiln as said deposit can be `expected to develop and a steel pipe 4 of the same diameter as that of said bore is inserted therein and welded to the wall of kiln.

As for the size, number and intervals of bores 3, the base of such space is selected as shown in FIG. 3 as the deposit may drop off naturally in time without ever growing until the operation of the rotary kiln lhas to be modified in any way and thus such selection must be made beforehand, in consideration of the strength, property, quantity and scope of adhesion of said deposit.

Next it is necessary to lill in some wadding (mortar,

etc.) in said bore 3 or insert an operative element or rod 5 therein beforehandso that said bore can be closed for the purpose of not disturbing the operation of the rotary kiln.

The diameter of the rod must be made a little smaller than said bore, in view of the heating expansion and the resul-ting space between both ldiameters is till-ed with `some tire-.proof material such as mortar. Although it is not necessary to limit its length, it may be two or three times as long as the'thicknessuof the rotary wall. The material of which rod 5 is made will be ordinary steel, heat-proof steel or some special steel, according to the strength of said deposit, its property or the method of operation. The operation of the rotary kiln can be started with bore 3 filled with wadding or with rod 5 inserted therein. In this case, the tip end of the operative element must be checked to remain at t-he surface of the inner lining of the rotary kiln.

Even when some deposit begins to grow at such places expected as'mentioned above, it is not necessary to reduce the speed of revolution of the rotary kiln or stop its revolution, but said operative element has `only to be pushed inside after destroying said wadding if already lilled, duringv the normal revolution of the rotary kiln so that the deposit can be dropped by said thrust of the operative element. As compared with deposits already attached to the inside of the rotary kiln after completion of manufacturing operation, those growing under high temperature during the operation of the rotary kiln are extremely soft and brittle so as to be destroyed in a simple manner by being pushed from the side of the rotary kiln.

The tip end of the operative element, after dropping the inner lining, as originally scheduled. As shown in said deposit, will be arranged to remain at the surface of FIG. 3, there are formed concave and convex portions on the deposits ranging over the expected space and then the convex portions are subjected to higher temperature by the burner c than the concave portions so that the variations in temperature between the concave and convex portions lead to slow-down of formation or adhesion of the deposits thereafter. In Iparticular, the adhesion of the concave portions becomes lessened and the adhesion of the convex portions becomes liable to drop off naturally until such deposits cannot grow to any larger degree than a fixed thickness. Thus by merely pushing all the operative elements arranged at such specified space in a repeated manner, it is possible to remove said deposits from the inside of the rotary kiln sufciently and effectively. Therefore, the operation of the rotary kiln can be continued safely without being disturbed by such deposits.

Next, an embodiment of the first method, according to the present invention will be explained.

In the case of manufacturing burnt crystal iron from limonite by the operation of a rotary kiln of 2.3 m. diameter x 38 m. length, there are provided 12 pierced bores of 1.5" at the wall of the rotary kiln at intervals of approximately 2 m. on the circumference of the kiln and at intervals of 1 meter over the length of the kiln between and 7 meters from the outlet of the rotary kiln. Then such deposits as are attached to the wall can be removed by pushing the operative elements in a repeated manner. The results of said operation are shown in FIG. 7. In the case of ordinary processes of conventional type, the working days per unit are 2O days out of which net 15 days only can be calculated as actually workable days (5 days are required to remain as after-completion days of operation and 7 hours are also required to heat the rotary kiln up to its succeeding operation and hence, to be exact, 14 days and 17 hours are summed up as actually workable days, i.e., 15 days as almost justified).

In contrast, according to the present invention, it requires no period of after-completion days so that approximately 5 days can be added to what is needed above, along with which every kind of manufacturing unit cost can be reduced. Its results are itemized as follows:

Percent (l) Increase in output 25 (2) Decrease in manufacturing unit cost:

Fuel 15 Electricity 15 Labor 15 Brickets Repair 5 As a further improved alternative of the first method of operation, the second method of operation can be carried out in the following way: Said operative elements in the first method are replaced by so many gunpowder filled-in elements which are subjected to natural explosion by the temperature inside the rotary kiln, in order to remove deposits attached to the rotary kiln. According to this second method -of operation, it has an advantage that deposits attached to the kiln can be removed at times by maintaining the normal revolution of the kiln during its operation. With reference to the accompanying drawings, this mechanism is explained as follows. As shown in FIG. 4, a brace of metal 7 is fixedly welded to the iron crust 1 around the pierced bore 4 as shown in the first method of operation. Therefore, besides the operative element 5, it is necessary to prepare a gun powder element 8 as shown in FIG. 5. This gunpowder element 8 is made of a meeting element 9 at its end to meet the brace of metal 7 and an element base 10 the tip end of which is provided with a case 11 in which a gunpowder case 12 is inserted.

The whole length of said gunpowder element may be almost the same as the above-mentioned operative element. Said gunpowder case 12 is an open-andclose container made of an iron pipe and its length may be determined, depending on the content of gunpowder inside. Moreover, the kind and quantity of gunpowder for use may be determined, according to the temperature inside the rotary kiln, the property of deposit and its quantity. By the way, said case 11 is made of a thin iron sheet etc., which may serve to support the inside content 13 and connect said gunpowder 12 to said gunpowder element 10. Its length may be arranged in proportion to the quantity of such inside content as mentioned above. Such inside content may be clay in most cases and its quantity can be determined according to the quantity of gunpowder and its quantity for use. While the gunpowder element 10 may be of the same diameter and quality as said operative element 5, its length must be made such, when its tip end remains on the surface of inner lining of the kiln, that the head of said gunpowder element can be simply inserted in the brace of metal 7 outside the rotary kiln.

The brace of metal 7 upon explosion must be strong enough to suppress the head of the gunpowder element 10 and match the force of such explosion. After filling the pierced bore 4 with some wadding or inserting an operative element in it, the operation of the rotary kiln may be commenced as usual. When some deposit begins to grow at such specified place as scheduled, it is not necessary to reduce the speed of revolution of the kiln or stop its revolution either, but the operative element 5 has only to be pushed inwardly to remove the deposit, even during the normal revolution of the kiln. Yet, whenever and wherever the deposit has grown up to such a thickness or rigidity as the operative element 5 alone cannot remove it, said operative element 5 must be replaced by the gunpowder element 8 immediately and then the base portion 9 of the element is caused to engage the brace of metal 7. By this means the gunpowder inserted in the gunpowder case 12 will explode naturally in a few minutes so that the deposit attached thereto can be destroyed and removed.

After completion of this procedure, the gunpowder element 10 will be replaced by the operative element 5 again. By means of said explosive operation, there are formed concave and convex portions on the deposit over such specified space almost to the same degree as shown in the first method of operation or sometimes more so than the latter. When these concave and convex portions have been formed, the concave ones are subjected to a relatively low temperature whereas the convex ones are subjected to a higher temperature. Thus according to variations in temperature between these portions, the adhesion of any such deposit will slow down extremely thereafter. In particular, the adhesion of the concave portions is very slow and that of the convex ones leads to many opportunities of natural drop or such deposits on the convex portions are not likely to develop in growth any more than up to a fixed thickness. Thus by giving such explosive operation to each bore proper in order ranging over a specified space, it is made possible to remove all such deposits inside the rotary kiln very effectively. Overall operation of the rotary kiln can be effected smoothly without being disturbed by such deposits and its stable and continuous operation be achieved.

In addition, it is desirable to select the material of said operative element according to the temperature inside the rotary kiln or its atmosphere beforehand and also to project the end of said operative element 10 from the surface of the inner lining of the kiln to such an extent as the length of the gunpowder case 12 and inside content 13, from the beginning. By this means, in the event of pulling out the operative element 5 there is already provided a spa-ce to permit the insertion of the gunpowder case 12 right away so that the insertion of the gunpowder-lled-'in element can be achieved in a simple manner. An experimental example of this operation is shown below.

In the case of manufacturing iron sinter from limonite by the use of a rotary kiln of 2.3 m. in diameter X 38 rn. in length, there are provided 12 pierced bores of 1.5 in diameter at intervals of approximately 2 m. on the circumference and approximately l m. over the length of the rotary kiln, and in place of operative elements for the removal of deposits, gunpowder 35 g. encased in so many gunpowder cases are used as inserted in the rotary kiln. Then the consumption of pieces only per pierced bore for a month can result in a very stable operation of the rotary kiln extending over the whole period of operation.

As the result of extension of the workable days and reduction in adjustment of temperature of the rotary kiln, nearly the same results of work can be obtained as those shown in the rst method of operation, in contrast to ordinary processes hitherto. Namely, its results are itemized as follows:

Percent (1) Increase in output 25 (2) Decrease in manufacturing unit cost:

Fuel Electricity 15 Labor 15 Bricks 10 Repair 5 comprising the steps of, removing each said first plug in succession from its bore, inserting into said bore a second plug having an explosive charge at its tip, to locate said explosive charge within the space in said ring vacated by said first plug, fixing the radially-outward end of said second plug against radially-outward movement, and effecting explosion of said explosive tip to thereby fracture, loosen and free from said lining, the contiguous portion of said ring.

2. The method of claim 1, explosion of said charge being effected by the heat of said ring surrounding the sarne.

3. The method of claim 1, said method being carried out while said ring is rotating.

4. A rotary kiln comprising a cylindrical metallic wall having a lining of refractory material and a plurality of spaced bores at selected points over an area where a fire ring accumulates in said kiln during production, each said bore extending through said wall and lining, a plurality of lirst rod-like elements, each slidably fitting and plugging a respective one of said bores, and means secured to the kiln and rigidly engaging the radially-outward end of each said element to releaseably hold each said element against movement in and along its bore.

5. The kiln of claim 4, the radially inward end of each said element projecting into said kiln, beyond said lining, when said element is held by said interengaging means.

References Cited by the Examiner UNITED STATES PATENTS 144,843 11/1873 Goldsmith et al. 134-17 X 292,305 1/ 1884 Hartman 75-41 868,904 10/ 1907 Bardill 266-42 1,117,814 11/1914 Dutton. 1,927,059 9/ 1933 Bahlke. 2,301,855 11/1942 Clif-fe 263-52 X 2,518,636 8/ 1950 Phillips 202-241 X 2,563,131 8/1951 Old 75-41 X 2,664,284 12/ 1953 Fausnaught 263-45 X 2,840,365 6/ 1958 Kruk 263-45 JOHN F. CAMPBELL, Primary Examiner.

RAY K. WINDHAN, DELBERT E. GANZ, MORRIS O. WOLK, Examiners. 

1. THE METHOD OF FREEING THE INTERIOR OF A ROTARY KILN, OF A FIRE RING ACCUMULTED THEREIN, SAID KILN INCLUDING A CYLINDRIDAL METALLIC WALL HAVING AN INTERIOR LINING OF REFRACTORY MATERIAL, THERE BEING A PLURALITY OF SPACED BORES THROUGH SAID WALL AND LINING OVER THE ARA WHERE SAID RING ACCUMULATES, EACH SAID BORE BEING FILLED WITH A RESPECTIVE FIRST PLUG OF HEAT-RESISTING MATERIAL, THE RADIALLYINWARD END OF EACH SAID FIRST PLUG PROJECTING INTO SAID KILN BEYOND THE INNER SURFACE OF SAID LINING, SAID METHOD COMPRISING THE STEPS OF, REMOVING EACH SAID FIRST PLUG IN SUCCESSION FROM ITS BORE, INSERTING INTO SAID BORE A SECOND PLUG HAVING AN EXPLOSIVE CHARGE AT ITS TIP, TO LOCATE SAID EXPLOSIVE CHARGE WITHIN THE SPACE IN SAID RING VACATED BY SAID FIRST PLUG, FIXING THE RADIALLY-OUTWARD END OF SAID SECOND PLUG AGAINST RADIALLY-OUTWARD MOVEMENT, AND EFFECTING EXPLOSIONS OF SAID EXPLOSVIE TIP TO THEREBY FRACTURE, LOOSEN AND FREE FROM SAID LINING, THE CONTIGUOUS PORTION OF SAID RING.
 4. A ROTARY KILN COMPRISING A CYLINDRICAL METALLIC WALL HAVING A LINING OF REFRACTORY MATERIAL AND A PLURALITY OF SPACED BORES AT SELECTED POINTS OVER AN AREA WHERE A FIRE RING ACCUMULATES IN SAID KILN DURING PRODUCTION, EACH SAID BORE EXTENDING THROUGH SAID WALL AND LINING, A PLURALITY OF FIRST ROD-LIKE ELEMENTS, EACH SLIDABLY FITING AND PLUGGING A RESPECTIVE ONE OF SAID BORES, AND MEANS SECURED TO THE KILN AND RIGIDLY ENGAGING THE RADIALLY-OUTWARD END OF EACH SAID ELEMENT TO RELEASEABLY HOLD EACH SAID ELEMENT AGAINST MOVEMENT IN AND ALONG ITS BORE. 